Combustion system, boiler system, and method for operating combustion system

Abstract

The purpose of the present invention is to appropriately reuse ammonia discharged from a fuel supply system with a simple configuration. A combustion system is provided with: a burner (21D) that combusts ammonia and forms a flame in a furnace; a combustion gas passage through which combustion gas generated in the furnace flows; an ammonia fuel supply system (210) that supplies ammonia as a fuel to the burner (21D); a purge gas line (221) that supplies purge gas to the ammonia fuel supply system (210), said purge gas causing ammonia to be discharged from the ammonia fuel supply system (210); and an ammonia supply system (220) that supplies ammonia discharged from the ammonia fuel supply system (210) to the inside of the combustion gas passage.

Description

Technical Field

[0001] The invention relates to a combustion system, a boiler system and an operating method of the combustion system. Background Art

[0002] Large boilers, such as those used for power generation, have a hollow, vertically arranged furnace. Multiple burners are arranged in the furnace wall along its circumference. Furthermore, a flue is connected vertically above the furnace. A heat exchanger for generating steam is located within this flue. The burners inject a mixture of fuel and air (oxidizing gas) into the furnace, creating a flame that generates combustion gases that flow into the flue. A heat exchanger is located in the area where the combustion gases flow, heating water or steam flowing within the heat transfer tubes that constitute the heat exchanger to generate superheated steam.

[0003] In recent years, a technique for using ammonia fuel as a fuel for steam generation in boilers, instead of coal fuel, has been proposed as an effective decarbonization technology (see, for example, Patent Document 1). The boiler disclosed in Patent Document 1 supplies ammonia fuel to a burner from an ammonia supply mechanism and coal fuel to a burner from a coal supply mechanism, and the ammonia fuel and coal fuel are mixed and burned in the boiler's furnace.

[0004] Previous technical literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-112280 Summary of the Invention

[0007] Technical issues to be solved by the invention

[0008] When ammonia fuel is supplied from an ammonia supply mechanism to a burner, for example, when combustion of the ammonia fuel in a boiler is stopped, it may be necessary to appropriately discharge the ammonia fuel remaining within the ammonia supply mechanism. In this case, a method can be considered, for example, to displace the ammonia fuel using a purge gas (e.g., nitrogen) and discharge it to a recovery facility. When the ammonia fuel discharged to the recovery facility is discarded, a device for detoxifying it is required. While it is possible to reuse the ammonia fuel discharged to the recovery facility, this requires, for example, treatment to remove nitrogen mixed with the ammonia fuel, potentially complicating the system due to the installation of the necessary recycling equipment.

[0009] Furthermore, the combustion gas generated in the boiler contains NOx. Therefore, in order to release the combustion gas to the outside, it is necessary to treat the NOx contained in the combustion gas. Therefore, a denitrification device for treating NOx is usually installed in the boiler. In a boiler that uses ammonia as fuel, the NOx contained in the combustion gas may increase compared to the case of burning traditional fuels (for example, coal, etc.). Therefore, when converting an existing boiler that burns traditional fuels into a boiler that uses ammonia as fuel, the existing denitrification device may have insufficient denitrification capacity. Taking this into account, when modifying the boiler, it is also possible to consider modifying the denitrification device. However, when the denitrification device is modified to improve the denitrification performance, there is a possibility that the modified denitrification device will become large-scale and complex.

[0010] Alternatively, a denitration method that does not utilize a denitration device could involve adding an externally introduced reducing agent to the combustion gas within the furnace. However, this method may complicate the system due to the installation of a device for externally supplying the reducing agent. This problem is particularly significant in boilers fueled by ammonia, as described above, because the amount of NOx contained in the combustion gas generated within the boiler tends to increase.

[0011] The present invention has been made in view of such circumstances, and an object of the present invention is to provide a combustion system, a boiler system, and a combustion system operating method that can appropriately reuse ammonia discharged from a fuel supply system with a simple structure.

[0012] Means for solving technical problems

[0013] In order to solve the above-mentioned problems, the combustion system, boiler system, and combustion system operating method of the present invention adopt the following means.

[0014] A combustion system according to one embodiment of the present invention comprises: a burner that burns ammonia to form a flame in a furnace; a combustion gas circulation portion through which combustion gas generated in the furnace circulates; an ammonia fuel supply system that supplies ammonia as fuel to the burner; a purge gas supply portion that supplies a purge gas to the ammonia fuel supply system to discharge ammonia from the ammonia fuel supply system; and an ammonia supply portion that supplies ammonia discharged from the ammonia fuel supply system to the interior of the combustion gas circulation portion.

[0015] In an operating method of a combustion system involved in one embodiment of the present invention, the combustion system comprises: a burner that burns ammonia to form a flame in a furnace; a combustion gas circulation portion through which the combustion gas generated in the furnace circulates; an ammonia fuel supply system that supplies ammonia as fuel to the burner; and a purge gas supply portion that supplies a purge gas to the ammonia fuel supply system to discharge ammonia from the ammonia fuel supply system. The operating method of the combustion system comprises: an ammonia supply process for supplying ammonia discharged from the ammonia fuel supply system to the interior of the combustion gas circulation portion.

[0016] Effects of the Invention

[0017] According to the present invention, ammonia exhausted from a fuel supply system can be appropriately reused with a simple structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic structural diagram showing a boiler according to the first embodiment of the present invention.

[0019] Figure 2 This is a schematic configuration diagram showing a fuel supply system in a boiler system according to the first embodiment of the present invention.

[0020] Figure 3 This is a block diagram showing a control device in the boiler system according to the first embodiment of the present invention.

[0021] Figure 4 This is a graph showing changes per unit time in the amount of ammonia fed, the amount of NOx at the inlet of the denitrification device, and the amount of ammonia at the inlet of the denitrification device in the boiler system according to the first embodiment of the present invention.

[0022] Figure 5 It is a schematic configuration diagram showing a fuel supply system in a boiler system according to a second embodiment of the present invention. DETAILED DESCRIPTION

[0023] Hereinafter, embodiments of a combustion system, a boiler system, and a combustion system operating method according to the present invention will be described with reference to the accompanying drawings.

[0024] [First embodiment]

[0025] The following describes a first embodiment of the present invention with reference to the accompanying drawings. The present invention is not limited to this embodiment and, when multiple embodiments are provided, also includes configurations combining the various embodiments. In the following description, "up" or "above" refers to the upper side in the vertical direction, and "down" or "below" refers to the lower side in the vertical direction. The vertical direction is not strictly defined as a vertical direction and includes errors.

[0026] Figure 1This is a schematic diagram showing the configuration of a boiler using solid fuel as a main fuel according to this embodiment.

[0027] The boiler 10 of this embodiment is a boiler capable of burning pulverized fuel (made by pulverizing solid fuel) and ammonia fuel containing ammonia in a burner, and exchanging the heat generated by this combustion with feedwater or steam to generate superheated steam. In other words, the boiler 10 is an ammonia-co-fired boiler. For example, the boiler 10 can be an ammonia-co-fired boiler with a high ammonia ratio. A high ammonia-co-fired boiler is one in which the ratio of ammonia fuel to the total fuel is 20% or greater. Biomass fuel, coal, or the like is used as the solid fuel.

[0028] The boiler 10 includes a furnace 11, a combustion device 20, and a combustion gas passage 12. The furnace 11 is a hollow square cylinder, arranged vertically. The furnace wall 101, which forms the inner surface of the furnace 11, is composed of a plurality of heat transfer tubes and fins connecting the tubes. Heat generated by the combustion of pulverized fuel and ammonia fuel is recovered through heat exchange with water or steam flowing through the heat transfer tubes, while also suppressing temperature increases in the furnace wall 101.

[0029] The combustion device 20 is installed in the lower area of ​​the furnace 11. In this embodiment, the combustion device 20 has a plurality of burners 21A, 21B, 21C, and 21D (hereinafter sometimes collectively referred to as "burners 21") installed on the furnace wall 101. The burners 21 are arranged in multiple stages in the vertical direction with burners arranged at equal intervals along the circumference of the furnace 11 (for example, four burners are arranged at each corner of the quadrilateral furnace 11). In addition, Figure 1 For ease of illustration, only two burners in one set are shown, and each set is labeled 21A, 21B, 21C, and 21D. The shape of the furnace, the number of burner stages, the number of burners in one stage, the arrangement of the burners, etc. are not limited to this embodiment.

[0030] Burners 21A, 21B, 21C, and 21D are connected to multiple fuel supply units 31A, 31B, 31C, and 31D (hereinafter sometimes collectively referred to as “fuel supply units 31 ”) via multiple fuel supply pipes 22A, 22B, 22C, and 22D (hereinafter sometimes collectively referred to as “fuel supply pipes 22 ”).

[0031] The fuel supply units 31A, 31B, and 31C are, for example, vertical roller mills. A pulverizing table (not shown) is rotatably supported within the mill, and multiple pulverizing rollers (not shown) are supported above the pulverizing table so as to rotate in conjunction with the table. The solid fuel pulverized by the pulverizing rollers and pulverizing table is conveyed to a classifier (not shown) within the fuel supply units 31A, 31B, and 31C via primary air (conveying gas, oxidizing gas) supplied to the fuel supply units 31A, 31B, and 31C. The classifier classifies the solid fuel into fine powder fuel with a particle size smaller than that suitable for combustion in the burners 21A, 21B, and 21C, and coarse powder fuel with a larger particle size. The fine powder fuel is then supplied to the burners 21A, 21B, and 21C along with the primary air via the fuel supply pipes 22A, 22B, and 22C. The coarse powdered fuel that has not passed through the classifier falls onto the pulverizing table due to its own weight inside the fuel supply parts 31A, 31B, and 31C, and is pulverized again.

[0032] The fuel supply unit 31D supplies ammonia fuel containing ammonia to the burner 21D. The ammonia fuel is supplied to the burner 21D via the fuel supply pipe 22D. The supply of the ammonia fuel including the fuel supply unit 31D and the fuel supply pipe 22D will be described later.

[0033] In the boiler system 100 of this embodiment, the boiler 10 generates steam by burning ammonia fuel (first fuel) with the burner (first burner) 21D and burning pulverized fuel (second fuel) with the burners (second burners) 21A, 21B, and 21C. The number and arrangement of the first and second burners are not limited to Figure 1 In the boiler system 100 of this embodiment, the fuel supply unit 31D and the fuel supply pipe 22D constitute an ammonia fuel supply system (a first fuel supply system) that supplies ammonia fuel to the burner 21D. Furthermore, in the boiler system 100 of this embodiment, the fuel supply units 31A, 31B, and 31C and the fuel supply pipes 22A, 22B, and 22C constitute a pulverized fuel supply system (a second fuel supply system) that supplies pulverized fuel to the burners 21A, 21B, and 21C.

[0034] A wind box (air conditioner) 23 is installed outside the furnace 11 at the location where the burner 21 is installed. One end of an air duct (air conduit) 24 is connected to the wind box 23. A forced draft fan (FDF) 32 is connected to the other end of the air duct 24. Air supplied from the forced draft fan 32 is heated by an air preheater 42 (described in detail later) installed in the air duct 24. The air is then supplied to the burner 21 as secondary air (combustion air, oxidizing gas) via the wind box 23 and then introduced into the furnace 11.

[0035] The combustion gas passage 12 is connected to the upper part of the furnace 11 in the vertical direction. The combustion gas passage 12 is provided with a superheater 102, a reheater 103, and an economizer 104 as heat exchangers for recovering the heat of the combustion gas. The combustion gas generated in the furnace 11 exchanges heat with the feed water or steam flowing through the interior of each heat exchanger. In addition, the arrangement and shape of each heat exchanger are not limited to Figure 1 The recorded method.

[0036] A flue 13 is connected to the downstream side of the combustion gas passage 12, which discharges the combustion gas, which has recovered heat through a heat exchanger. An air preheater (air heater) 42 is installed between the flue 13 and the air duct 24. This air preheater (air heater) 42 exchanges heat between the air flowing through the air duct 24 and the combustion gas flowing through the flue 13. This air preheater heats the primary air supplied to the fuel supply units 31A, 31B, and 31C, or the secondary air supplied to the burner 21, thereby further recovering heat from the combustion gas after heat exchange with water or steam.

[0037] Furthermore, a denitrification device 43 may be installed in the flue 13 at a position upstream of the air preheater 42. The denitrification device 43 supplies a reducing agent, such as ammonia or urea water, to the combustion gas flowing through the flue 13. The denitrification catalyst installed in the denitrification device 43 promotes the reaction between nitrogen oxides (NOx) in the combustion gas to which the reducing agent is supplied and the reducing agent, thereby removing and reducing the nitrogen oxides in the combustion gas.

[0038] A gas duct 41 is connected to the flue 13 downstream of the air preheater 42. Gas duct 41 is equipped with a dust collector 44, such as an electrostatic precipitator, to remove dust and other particles from the combustion gas, and a desulfurizer 46, which removes sulfur oxides. An induced draft fan (IDF) 45 is also installed to direct the exhaust gas to these environmental devices. The downstream end of gas duct 41 is connected to a chimney 47, and the combustion gas processed by the environmental devices is discharged outside the system as exhaust gas.

[0039] In boiler 10, when fuel supply unit 31 (31A, 31B, 31C) is driven, crushed and classified pulverized fuel is supplied to burner 21 along with primary air via fuel supply pipe 22 (22A, 22B, 22C). Secondary air heated by air preheater 42 is then supplied to burner 21 from air duct 24 via wind box 23. Burners 21 (21A, 21B, 21C) blow a pulverized fuel mixture, formed by mixing pulverized fuel and primary air, into furnace 11 and also blow secondary air into furnace 11. The pulverized fuel mixture blown into furnace 11 is ignited and reacts with the secondary air, forming a pulverized fuel flame.

[0040] In boiler 10, when using ammonia fuel, the ammonia fuel is supplied from fuel supply unit 31D via fuel supply pipe 22D to burner 21D. Furthermore, secondary air heated by air preheater 42 is supplied from air duct 24 via wind box 23 to burner 21D. Burner 21D blows the ammonia fuel into furnace 11, and also blows the secondary air into furnace 11. The ammonia fuel blown into furnace 11 reacts with the secondary air, forming an ammonia fuel flame.

[0041] In the lower region of furnace 11, a flame of pulverized fuel and ammonia fuel forms, and high-temperature combustion gases rise within furnace 11 and flow into combustion gas passage 12. In this embodiment, air is used as the oxidizing gas (primary air, secondary air), but gases with a higher or lower oxygen content than air may also be used, and the ratio of oxygen content to the amount of supplied fuel may be adjusted within an appropriate range to achieve stable combustion in furnace 11.

[0042] Furthermore, a plurality of additional air ports (air supply units) 25 for supplying additional air (AA) for combustion into the furnace 11 are provided above the location where the burners 21 of the furnace 11 are mounted. The ends of additional air ducts 26 branching from the air duct 24 are connected to the additional air ports 25. A portion of the air supplied by the forced draft fan 32 can be supplied to the additional air ports 25 via the additional air ducts 26 as additional air for combustion.

[0043] exist Figure 1In the illustrated furnace 11, in region A (corresponding to the height range of the wind box 23), a flame is formed by the combustion of a mixture of primary air and pulverized fuel with secondary air. By setting the air ratio in region A to less than 1—specifically, by setting the amount of air supplied to the burner 21 (the total of primary and secondary air) to less than the theoretical amount of air relative to the amount of fuel supplied to the burner 21—a reducing atmosphere is created in regions A and B (the region from the top of the burner 21 to the bottom of the additional air port 25) within the furnace 11. Nitrogen oxides (NOx) generated by combustion are reduced within the furnace 11. Subsequently, in region C (above the bottom of the additional air port 25), additional combustion air is supplied from the additional air port 25 to the reduced combustion gas, completing the combustion. However, NOx generation is reduced by an amount equivalent to the reduction effect in regions A and B.

[0044] On the downstream side of the region C, an ammonia nozzle 51 to be described later is provided.

[0045] The combustion gas flowing into the combustion gas passage 12 undergoes heat exchange with water or steam in the superheater 102, reheater 103, and economizer 104 located within the combustion gas passage 12. The combustion gas is then discharged into the flue 13, where nitrogen oxides are removed by the denitrification unit 43. The gas then undergoes heat exchange with primary and secondary air in the air preheater 42 before being discharged into the gas duct 41. Ash and other substances are removed by the dust collector 44, and sulfur oxides are removed by the desulfurization unit 46. The gas is then discharged to the outside of the system through a chimney 47. The arrangement of the various heat exchangers in the combustion gas passage 12 and the various devices in the flue 13 and gas duct 41 does not necessarily have to follow the order of the combustion gas flow described above.

[0046] Next, the ammonia fuel supply system 210 and the ammonia supply system 220 in the boiler system 100 according to the first embodiment of the present invention will be described. Figure 2 1 is a schematic diagram showing the configuration of the ammonia fuel supply system 210 and the ammonia supply system 220 in the boiler system 100 according to the first embodiment of the present invention. Figure 2 As shown, the boiler system 100 of this embodiment includes an ammonia fuel supply system 210, an ammonia supply system 220, and a control device 200 (see Figure 3 The boiler system 100 according to the present embodiment supplies gaseous ammonia fuel (a combustible material containing ammonia as a component and supplied to the burner 21D in a gaseous state, hereinafter referred to as “ammonia gas”) as fuel to the boiler 10 .

[0047] like Figure 2As shown, the ammonia fuel supply system 210 is a system that supplies ammonia fuel (ammonia gas in this embodiment) containing ammonia to the burner 21D. Figure 1 The ammonia fuel supply system 210 includes an ammonia fuel tank 211 , a pump 212 , a heater 213 , an on-off valve 214 , a control valve 215 , and a burner valve 27 . These components are controlled by the control device 200 .

[0048] The ammonia fuel tank 211 is a container for storing ammonia gas supplied from an ammonia fuel supply source. The ammonia gas stored in the ammonia fuel tank 211 is supplied to a heater 213 by a pump 212. The heater 213 heats the ammonia gas to a temperature suitable for combustion in the burner 21D. The ammonia gas heated by the heater 213 is supplied to the burner 21D via a fuel supply line 210a. The boiler 10 generates steam by burning the ammonia fuel supplied as ammonia gas through the burner 21D. Depending on the properties of the ammonia fuel used, the heater 213 may be omitted.

[0049] Alternatively, liquid ammonia fuel may be supplied from an ammonia fuel supply source. In this case, liquid ammonia fuel is stored in an ammonia fuel tank 211 and supplied to a heater 213 by a pump 212. The liquid ammonia fuel is heated in the heater 213, thereby converting the liquid fuel into a gaseous state and supplying the gas to the burner 21D.

[0050] The fuel supply line 210a is provided with an on-off valve 214, a control valve 215, and a burner valve 27. The on-off valve 214 is a device that is opened when ammonia gas is supplied to at least one of the multiple burners 21D, and is closed when ammonia gas is not supplied to all burners 21D. The control valve 215 is a device for adjusting the amount of ammonia gas supplied to the burner 21D when the on-off valve 214 is open. The burner valve 27 is provided for each burner 21D and is opened when ammonia gas is supplied to the burner 21D, and is closed when ammonia gas is not supplied to the burner 21D.

[0051] The fuel supply line 210a connects the ammonia fuel tank 211 and the boiler 10 (more specifically, the burner 21D). The fuel supply line 210a branches into a circulation line 210b at a position downstream of the control valve 215. The circulation line 210b connects the fuel supply line 210a and the ammonia fuel tank 211. The circulation line 210b guides a portion of the ammonia gas flowing in the fuel supply line 210a to the ammonia fuel tank 211. An on-off valve 216 is provided in the circulation line 210b. The on-off valve 216 is a device that is in an open state when ammonia gas is circulated to the ammonia fuel tank 211 and is in a closed state when ammonia gas is not circulated to the ammonia fuel tank 211. The circulation line 210b is used to suppress the pressure drop when the burner 21D is ignited. The circulation line 210b can be omitted. Furthermore, when liquid ammonia fuel is stored in the ammonia fuel tank 211 , a cooler (not shown) for re-liquefying the gaseous ammonia fuel is provided in the circulation line 210 b .

[0052] The boiler system 100 includes a purge gas line 221 for supplying a purge gas (e.g., nitrogen) to the ammonia fuel supply system 210. Purge gas supplied from a purge gas supply source flows through the purge gas line 221. A purge gas valve 221a is provided in the purge gas line 221. The downstream end of the purge gas line 221 is connected to the ammonia fuel supply system 210. Specifically, the downstream end of the purge gas line 221 is connected to the fuel supply line 210a. In addition, the portion to which the downstream end of the purge gas line 221 is connected is not limited to the fuel supply line 210a. For example, the downstream end of the purge gas line 221 may be connected to the ammonia fuel tank 211. Furthermore, the downstream end of the purge gas line 221 may be connected to both the fuel supply line 210a and the ammonia fuel tank 211.

[0053] The ammonia supply system 220 is a system that guides the ammonia gas supplied to the ammonia fuel supply system 210 to the combustion gas passage 12 of the boiler 10 via the ammonia recovery tank 226 and reduces NOx contained in the combustion gas.

[0054] The ammonia supply system 220 has a first exhaust pipe 222 connected to the ammonia fuel tank 211, a second exhaust pipe 223 connected between the heater 213 and the on-off valve 214 of the fuel supply pipe 210a, a third exhaust pipe 224 connected to a position downstream of the branch point of the circulation pipe 210b of the fuel supply pipe 210a, and a fourth exhaust pipe 225 connected to the circulation pipe 210b.

[0055] A first exhaust valve 222a is provided in the first exhaust line 222. A second exhaust valve 223a is provided in the second exhaust line 223. A third exhaust valve 224a is provided in the third exhaust line 224. A fourth exhaust valve 225a is provided in the fourth exhaust line 225.

[0056] The downstream ends of the first exhaust line 222, the second exhaust line 223, the third exhaust line 224, and the fourth exhaust line 225 are connected to an ammonia exhaust line 227. The ammonia exhaust line 227 guides ammonia exhausted from the ammonia fuel supply system 210 via the purge gas to an ammonia recovery tank 226. A mixed gas of ammonia and the purge gas flows through the ammonia exhaust line 227. A control valve 227a is provided in the ammonia exhaust line 227.

[0057] The ammonia recovery tank 226 stores a mixed gas of ammonia gas and purge gas. An ammonia supply line 228 is connected to the ammonia recovery tank 226. The ammonia supply line 228 guides the mixed gas of ammonia gas and purge gas stored in the ammonia recovery tank 226 to the boiler 10. Specifically, the mixed gas is guided to the ammonia nozzle 51 (refer to Figure 1 ). That is, the ammonia supply line 228 branches at an intermediate position, and each downstream end is connected to a corresponding ammonia nozzle 51 among the plurality of ammonia nozzles 51 .

[0058] A fan 228a, a flow sensor 228b, an on-off valve 228d, and a control valve 228c are provided in the ammonia supply line 228, in this order from the upstream side. The fan 228a, flow sensor 228b, control valve 228c, and on-off valve 228d are controlled by the controller 200. The fan 228a is driven to rotate, causing the mixed gas to flow through the ammonia supply line 228. The flow sensor 228b measures the flow rate of the mixed gas flowing through the ammonia supply line 228. The control valve 228c adjusts the flow rate of the mixed gas (a mixture of ammonia and purge gas) flowing through the ammonia supply line 228 by adjusting its opening. In other words, the control valve 228c adjusts the amount of ammonia supplied from the ammonia nozzle 51 to the combustion gas passage 12 of the boiler 10 by adjusting its opening.

[0059] like Figure 1 As shown, a plurality of ammonia nozzles 51 are provided in the boiler 10. The ammonia nozzles 51 inject ammonia into the combustion gas flowing through the combustion gas passage 12. The ammonia nozzles 51 preferably inject ammonia into the combustion gas at a temperature range where the NOx reduction reaction by ammonia is active (e.g., approximately 1000°C).

[0060] The ammonia nozzle 51 is provided at a position downstream of the additional air port 25. For example, the ammonia nozzle 51 is provided upstream of the superheater 102 or downstream of the superheater 102 and upstream of the reheater 103.

[0061] The plurality of ammonia nozzles 51 are arranged at predetermined intervals in the direction in which the combustion gas flows, and are arranged in a row at predetermined intervals in a direction intersecting the direction in which the combustion gas flows. The position and number of the ammonia nozzles 51 are not limited to Figure 1The method shown is determined according to the size of the combustion gas channel 12 and the distribution of the combustion gas temperature.

[0062] The ammonia nozzle 51 denitrates the combustion gas by injecting ammonia gas into the combustion gas. Specifically, the ammonia nozzle 51 reduces NOx contained in the combustion gas by injecting ammonia gas into the combustion gas.

[0063] The purge gas valve 221a is controlled by the controller 200 to open when the supply of ammonia gas from the ammonia fuel supply system 210 to the burner 21D is stopped (in this case, the on-off valve 214 and the burner valves 27 of all burners 21D are closed) and ammonia gas is discharged from the ammonia fuel supply system 210. This supplies purge gas to the ammonia fuel supply system 210. Furthermore, when ammonia gas is discharged from the ammonia fuel supply system 210, the ammonia supply system 220 is controlled by the controller 200 to open the first exhaust valve 222a, the second exhaust valve 223a, the third exhaust valve 224a, and the fourth exhaust valve 225a.

[0064] The ammonia supply system 220 is controlled by the control device 200 to supply purge gas to the fuel supply line 210 a via the purge gas line 221 , and discharge ammonia remaining in the ammonia fuel supply system 210 to the ammonia recovery tank 226 via the ammonia discharge line 227 .

[0065] The ammonia supply system 220 is controlled by the control device 200 so that the mixed gas of ammonia and purge gas stored in the ammonia recovery tank 226 is supplied to the ammonia nozzle 51 of the boiler 10 through the ammonia supply pipe 228, and ammonia (mixed gas) is injected into the combustion gas channel 12 from the ammonia nozzle 51.

[0066] like Figure 1 As shown, in the boiler system 100, a NOx detection unit 52 and an ammonia detection unit 53 are provided on the downstream side of the economizer 104 and the upstream side of the denitrification device 43. The NOx detection unit 52 detects the amount of NOx contained in the combustion gas flowing between the economizer 104 and the denitrification device 43 (hereinafter referred to as "the amount of NOx at the inlet of the denitrification device"). In addition, the ammonia detection unit 53 detects the amount of ammonia contained in the combustion gas flowing between the economizer 104 and the denitrification device 43 (hereinafter referred to as "the amount of ammonia at the inlet of the denitrification device"). Figure 3 As shown, the NOx detection unit 52 and the ammonia detection unit 53 transmit the detected information to the control device 200 .

[0067] The control device 200 controls various devices such as valves and pumps provided in the boiler system 100 .

[0068] The control device 200 also includes an ammonia control unit 202. The ammonia control unit 202 adjusts the opening of the control valve 228c of the ammonia supply line 228 based on the NOx amount at the denitrification device inlet detected by the NOx detection unit 52 and the ammonia amount at the denitrification device inlet detected by the ammonia detection unit 53, thereby controlling the amount of ammonia introduced from the ammonia nozzle 51.

[0069] The controller 200 (Controller) includes, for example, a CPU (Central Processing Unit), a main memory, a secondary storage, etc. The controller 200 may also include a communication unit for transmitting and receiving information with other devices.

[0070] The main storage device is composed of a writable memory such as a cache memory or a RAM (Random Access Memory), and is used as a work area for reading execution programs of the CPU and writing processing data based on the execution programs.

[0071] A secondary storage device is a non-transitory computer-readable storage medium, such as a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, or a semiconductor memory.

[0072] For example, a series of processes for implementing various functions can be stored as a program in a secondary storage device, with the CPU loading the program into the primary storage device and executing information processing / arithmetic operations to implement the various functions. Alternatively, the program can be pre-installed in a secondary storage device, provided as stored on a computer-readable storage medium, or transmitted via wired or wireless communication means. Computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories.

[0073] Next, use Figure 4 The following describes changes in the amount of ammonia input, the amount of NOx at the inlet of the denitrification device, and the amount of ammonia at the inlet of the denitrification device when the ammonia control unit 202 performs a process for adjusting the amount of ammonia.

[0074] like Figure 4As shown, the boiler system 100 is controlled so that the NOx amount at the denitrification device inlet, as detected by the NOx detector 52, reaches a first set value N1 (before time T1) by adjusting the burner angle, AA angle, AA throttle valve opening, and other parameters. When ammonia is added from the ammonia nozzle 51 via the ammonia supply line 228 (time T1), the amount of ammonia added increases as the opening of the control valve 228c increases, and the NOx amount at the denitrification device inlet decreases from the first set value N1 (from time T1 to time T2).

[0075] When the NOx amount at the denitration device inlet reaches the second set value N2, the ammonia control unit 202 fixes the opening of the control valve 228c (time T2). As a result, the NOx amount at the denitration device inlet is maintained at the second set value N2.

[0076] For example, if the amount of ammonia at the denitrification device inlet increases (at time T3) due to changes in the ammonia concentration in the ammonia gas supplied from the ammonia nozzle 51, the amount of NOx at the denitrification device inlet decreases accordingly (from time T3 to time T4). If the amount of ammonia at the denitrification device inlet exceeds a predetermined threshold value A1, the ammonia control unit 202 determines that ammonia is being overdosed and reduces the opening of the control valve 228c to reduce the amount of ammonia gas added (at time T4). If the amount of NOx at the denitrification device inlet increases due to the reduction in the amount of ammonia gas added and reaches the second set value N2, the ammonia control unit 202 maintains the opening of the control valve 228c. As a result, the amount of NOx at the denitrification device inlet is maintained at the second set value N2.

[0077] Furthermore, for example, if the amount of ammonia at the denitrification device inlet decreases due to changes in the ammonia concentration in the ammonia gas supplied from the ammonia nozzle 51, the amount of NOx at the denitrification device inlet increases accordingly. If the amount of NOx at the denitrification device inlet exceeds the second set value N2, the ammonia control unit 202 increases the opening of the control valve 228c and increases the amount of ammonia gas fed. If the amount of NOx at the denitrification device inlet decreases due to the increase in the amount of ammonia gas fed and reaches the second set value N2, the ammonia control unit 202 maintains the opening of the control valve 228c. As a result, the amount of NOx at the denitrification device inlet is maintained at the second set value N2.

[0078] According to this embodiment, the following effects are achieved.

[0079] In this embodiment, an ammonia supply system 220 (particularly, an ammonia nozzle 51) is provided to supply ammonia discharged from the ammonia fuel supply system 210 via purge gas into the combustion gas passage 12 of the boiler 10. This allows ammonia discharged from the ammonia fuel supply system 210 to be supplied to the combustion gas flowing through the combustion gas passage 12. Consequently, ammonia discharged from the ammonia fuel supply system 210 can react with the combustion gas, reducing nitrogen oxides (NOx) contained in the combustion gas. In other words, denitrification of the combustion gas is achieved. Furthermore, the reaction between the combustion gas and ammonia decomposes the ammonia into nitrogen and water.

[0080] By utilizing ammonia discharged from the ammonia fuel supply system 210 as the reducing agent for denitrifying the combustion gas, the amount of reducing agent used in the boiler system 100 can be reduced compared to a case where the discharged ammonia is not utilized (where the reducing agent is supplied separately from an external source). This reduces operating costs. Furthermore, since a separate device for supplying the reducing agent from an external source can be eliminated or downsized, the structure of the boiler system 100 can be simplified. Consequently, initial costs can be reduced.

[0081] Furthermore, since ammonia discharged from the ammonia fuel supply system 210 reacts with the combustion gas to decompose it into nitrogen and water, there is no need to use a separate solution for decomposing ammonia. This reduces operating costs compared to using a separate solution for decomposing ammonia. Furthermore, since a separate device for decomposing the discharged ammonia can be omitted or miniaturized, the structure of the boiler system 100 can be simplified. This reduces initial costs.

[0082] Thus, in this embodiment, ammonia exhausted from the ammonia fuel supply system 210 can be appropriately reused with a simple structure. Therefore, costs can be reduced.

[0083] The supply of air from the additional air port 25 completes the combustion of the fuel within the furnace 11. Consequently, in the space downstream of the additional air port 25, the oxygen in the air introduced into the furnace 11 is consumed, reducing the oxygen concentration. In this embodiment, the ammonia supply system 220 (particularly the ammonia nozzle 51) supplies ammonia discharged from the ammonia fuel supply system 210 via purge gas to a location further downstream of the additional air port 25. This allows ammonia to be supplied to a space with a low oxygen concentration, thereby more effectively reducing NOx contained in the combustion gas.

[0084] Furthermore, because the reheater 103 and economizer 104 recover heat, the combustion gas temperature is higher in the space upstream of the reheater 103 and economizer 104 than in the space downstream of the reheater 103 and economizer 104. In this embodiment, the ammonia supply system 220 (particularly the ammonia nozzle 51) supplies ammonia discharged from the ammonia fuel supply system 210 via purge gas to a location upstream of the reheater 103 and economizer 104. This allows ammonia to be supplied to a space where the combustion gas temperature is high (for example, a space with a combustion gas temperature of approximately 1000°C), thereby more effectively reducing NOx contained in the combustion gas.

[0085] The concentration of ammonia contained in the fluid discharged from the ammonia fuel supply system 210 via the purge gas (a mixture of purge gas and ammonia, i.e., the mixed fluid) is not constant. Therefore, even if a constant amount of the mixed fluid is supplied to the combustion gas passage 12 via the ammonia supply system 220 (particularly the ammonia nozzle 51), the amount of ammonia supplied to the combustion gas passage 12 is not constant. Consequently, there is a possibility that the amount of ammonia supplied to the combustion gas passage 12 may become excessive or insufficient. In particular, if the amount of ammonia supplied to the combustion gas passage 12 becomes excessive, ammonia may remain in the combustion gas, potentially causing adverse effects such as the formation of ammonium sulfate in downstream equipment. In particular, there is a risk of clogging the air preheater 42.

[0086] Meanwhile, in this embodiment, a control device 200 is provided for controlling a control valve 228c of the ammonia supply line 228 based on information detected by the NOx detector 52. This allows the amount of ammonia supplied to the interior of the combustion gas passage 12 to be adjusted based on the amount of nitrogen oxides contained in the combustion gas. Therefore, for example, if the control device 200 controls the control valve 228c so that the amount of nitrogen oxides contained in the combustion gas falls within a predetermined range, an appropriate amount of ammonia can be supplied to the interior of the combustion gas passage 12.

[0087] Furthermore, in this embodiment, a control device 200 is provided for controlling a control valve 228c of the ammonia supply line 228 based on information detected by the ammonia detector 53. This allows the amount of ammonia supplied to the interior of the combustion gas passage 12 to be adjusted based on the amount of ammonia contained in the combustion gas. Therefore, for example, if the control device 200 controls the control valve 228c so that the amount of ammonia contained in the combustion gas falls within a predetermined range, an appropriate amount of ammonia can be supplied to the interior of the combustion gas passage 12. The predetermined range may be, for example, an ammonia amount sufficient to prevent the generation of ammonium sulfate in a device located downstream.

[0088] Furthermore, the NOx amount at the denitrification device inlet may fluctuate due to the fluctuation in the amount of ammonia supplied to the combustion gas passage 12. This may cause the operation of the denitrification device to become unstable, and the NOx amount at the denitrification device outlet may also fluctuate.

[0089] On the other hand, in this embodiment, the NOx amount at the denitrification device inlet is controlled to a predetermined amount. Therefore, the NOx amount at the denitrification device inlet can be stabilized, thereby stabilizing the operation of the denitrification device and suppressing fluctuations in the NOx amount at the denitrification device outlet.

[0090] [Second embodiment]

[0091] use Figure 5A second embodiment of the present invention will be described.

[0092] In this embodiment, the configuration described below is different from that of the first embodiment. Since the other configurations are the same as those of the first embodiment, the same reference numerals are given to the same configurations and detailed description thereof is omitted.

[0093] The ammonia fuel supply system 210 of the boiler system 100A according to this embodiment supplies liquid ammonia (a combustible material containing ammonia as a component and supplied to the burner 21D in a liquid state, hereinafter referred to as “liquid ammonia”) as fuel to the burner 21D of the boiler 10 .

[0094] The boiler system 100A according to the present embodiment includes an ammonia supply system 220A.

[0095] The ammonia supply system 220A includes an ammonia recovery tank 226A for storing liquid ammonia. Furthermore, the ammonia supply system 220A includes a first drain line 222A connected to the ammonia fuel tank 211, a second drain line 223A connected between the heater 213 and the on-off valve 214 of the fuel supply line 210a, a third drain line 224A connected downstream of the branch point of the circulation line 210b of the fuel supply line 210a, and a fourth drain line 225A connected to the circulation line 210b.

[0096] The first drain pipe 222A is provided with a first drain valve 222aA. The second drain pipe 223A is provided with a second drain valve 223aA. The third drain pipe 224A is provided with a third drain valve 224aA. The fourth drain pipe 225A is provided with a fourth drain valve 225aA.

[0097] The downstream ends of the first drain line 222A, the second drain line 223A, the third drain line 224A, and the fourth drain line 225A are connected to an ammonia discharge line 227A. Ammonia discharge line 227A guides ammonia discharged from the ammonia fuel supply system 210 via purge gas to an ammonia recovery tank 226A. A mixed two-phase flow of liquid ammonia and purge gas flows through ammonia discharge line 227A.

[0098] A mixed two-phase flow of liquid ammonia and purge gas is supplied to the ammonia recovery tank 226A. In the ammonia recovery tank 226A, the liquid ammonia and purge gas are separated, and the separated purge gas is discharged outside the system. An ammonia supply line 228A is connected to the ammonia recovery tank 226A. The ammonia supply line 228A directs the liquid ammonia, separated and stored from the purge gas in the ammonia recovery tank 226A, to the ammonia nozzle 51.

[0099] A pump 228aA and a control valve 228bA are provided in the ammonia supply line 228A, sequentially from the upstream side. Pump 228aA and control valve 228bA are controlled by the control device 200. Pump 228aA is driven to rotate, causing liquid ammonia to flow through the ammonia supply line 228A. Control valve 228bA adjusts the flow rate of liquid ammonia flowing through the ammonia supply line 228A by adjusting its opening. In other words, control valve 228bA adjusts the amount of ammonia supplied from the ammonia nozzle 51 to the combustion gas passage 12 of the boiler 10 by adjusting its opening.

[0100] The arrangement of the ammonia nozzle 51 and the control performed by the control device 200 are the same as those in the first embodiment, and therefore their description is omitted.

[0101] According to this embodiment, the following effects are achieved.

[0102] As in the present embodiment, also in the boiler system 100A in which ammonia liquid is supplied as fuel to the boiler 10 , the same effects as those of the first embodiment can be achieved.

[0103] The present invention is not limited to the above-described embodiment, and can be modified appropriately without departing from the spirit of the present invention.

[0104] In the above embodiment, the boiler of the present invention is described as a boiler that mixes solid fuel and ammonia fuel. Solid fuels used in the boiler include coal, biomass fuel, petroleum coke (PC), petroleum residue, and the like.

[0105] Furthermore, boiler fuel is not limited to solid fuels. Petroleum-based fuels such as heavy oil, light oil, and heavy oil, as well as liquid fuels such as factory wastewater, can be used. Furthermore, gaseous fuels such as natural gas, various petroleum gases, by-product gases generated in steelmaking processes, and hydrogen can also be used.

[0106] Furthermore, it can be applied to a mixed-fired boiler using a combination of these various fuels, or a dedicated boiler using only ammonia fuel.

[0107] For example, the position where the ammonia nozzle 51 is installed is not limited to the position described above. For example, it may be installed between the reheater 103 and the economizer 104. Alternatively, it may be installed between the economizer 104 and the denitrification device 43.

[0108] The combustion system, the boiler system, and the method of operating the combustion system described in the above-described embodiments can be understood, for example, as follows.

[0109] The combustion system involved in the first embodiment of the present invention includes: a burner 21D, which burns ammonia to form a flame in the furnace 11; a combustion gas circulation part 12, in which the combustion gas generated in the furnace circulates; an ammonia fuel supply system 210, which supplies ammonia as fuel to the burner; a purge gas supply part 221, which supplies a purge gas to the ammonia fuel supply system to discharge ammonia from the ammonia fuel supply system; and an ammonia supply part 220, which supplies ammonia discharged from the ammonia fuel supply system to the interior of the combustion gas circulation part.

[0110] The above structure includes an ammonia supply unit that supplies ammonia discharged from the fuel supply system to the interior of the combustion gas circulation unit. This allows ammonia discharged from the fuel supply system to be supplied to the combustion gas circulating within the combustion gas circulation unit. Consequently, the ammonia discharged from the fuel supply system can react with the combustion gas, reducing nitrogen oxides (NOx) contained in the combustion gas. In other words, denitrification of the combustion gas is achieved. Furthermore, the reaction between the combustion gas and ammonia decomposes the ammonia into nitrogen and water.

[0111] By utilizing ammonia emitted from the fuel supply system as the reducing agent for denitrifying combustion gas, the amount of reducing agent used in the combustion system can be reduced compared to a system that does not utilize the emitted ammonia (i.e., by supplying the reducing agent externally). This reduces running costs. Furthermore, since a separate device for supplying the reducing agent externally can be eliminated or downsized, the combustion system structure can be simplified. Consequently, initial costs can be reduced.

[0112] Furthermore, by reacting ammonia emitted from the fuel supply system with combustion gases to decompose it into nitrogen and water, there's no need to use a separate solution for decomposing ammonia. This reduces running costs compared to using a separate solution for decomposing ammonia. Furthermore, since a separate device for decomposing the emitted ammonia can be omitted or downsized, the combustion system can be simplified. Consequently, initial costs can be reduced.

[0113] Thus, in the above-mentioned structure, ammonia exhausted from the fuel supply system can be appropriately reused with a simple structure, thereby reducing costs.

[0114] Furthermore, the combustion system involved in the second embodiment of the present invention, in the above-mentioned first embodiment, comprises: a nitrogen oxide detection unit 52, which detects the amount of nitrogen oxides contained in the combustion gas flowing downstream of the ammonia supply unit; an adjustment unit 228c, which adjusts the amount of ammonia supplied to the inside of the combustion gas circulation unit through the ammonia supply unit; and a control unit 200, which controls the adjustment unit based on the information detected by the nitrogen oxide detection unit.

[0115] The concentration of ammonia contained in the fluid discharged from the fuel supply system by the purge gas (a mixture of purge gas and ammonia, or a mixed fluid) is not constant. Therefore, even if a constant amount of the mixed fluid is supplied to the combustion gas flow path by the ammonia supply unit, the amount of ammonia supplied to the combustion gas flow path is not constant. Consequently, there is a possibility that the amount of ammonia supplied to the combustion gas flow path may become excessive or insufficient. In particular, if the amount of ammonia supplied to the combustion gas flow path becomes excessive, ammonia may remain in the combustion gas, potentially causing adverse effects such as the formation of ammonium sulfate in downstream equipment.

[0116] The above configuration includes a control unit that controls the adjustment unit based on information detected by the nitrogen oxide detection unit. This allows the amount of ammonia supplied to the interior of the combustion gas circulation unit to be adjusted based on the amount of nitrogen oxides contained in the combustion gas. Therefore, for example, if the control unit controls the adjustment unit so that the amount of nitrogen oxides contained in the combustion gas is within a predetermined range, an appropriate amount of ammonia can be supplied to the interior of the combustion gas circulation unit.

[0117] In addition, the nitrogen oxide detection unit may measure the amount of NOx in the combustion gas, or may estimate the amount of NOx in the combustion gas based on other parameters.

[0118] Furthermore, the combustion system involved in the third embodiment of the present invention, in any of the above-mentioned first embodiment or second embodiment, comprises: an ammonia detection unit 53, which detects the amount of ammonia contained in the combustion gas flowing downstream of the ammonia supply unit; an adjustment unit 228c, which adjusts the amount of ammonia supplied to the interior of the combustion gas circulation unit through the ammonia supply unit; and a control unit 200, which controls the adjustment unit based on the information detected by the ammonia detection unit.

[0119] The above configuration includes a control unit that controls the adjustment unit based on information detected by the ammonia detection unit. This allows the amount of ammonia supplied to the interior of the combustion gas circulation unit to be adjusted based on the amount of ammonia contained in the combustion gas. Therefore, for example, if the control unit controls the adjustment unit so that the amount of ammonia contained in the combustion gas is within a predetermined range, an appropriate amount of ammonia can be supplied to the interior of the combustion gas circulation unit. The predetermined range may be, for example, an ammonia amount sufficient to prevent the generation of ammonium sulfate in a device located downstream.

[0120] In addition, the ammonia detection unit may measure the amount of ammonia in the combustion gas, or may estimate the amount of ammonia in the combustion gas based on other parameters.

[0121] Furthermore, the boiler system according to the first aspect of the present invention includes: the combustion system according to any one of the first to third aspects; and heat exchangers 102 , 103 , 104 provided in the combustion gas flow portion 12 for recovering heat of the combustion gas.

[0122] Furthermore, the boiler system involved in the second embodiment of the present invention is provided in the above-mentioned first embodiment with: an air supply section 25, which is arranged at a position further downstream of the combustion gas flow than the burner and supplies air into the furnace; the boiler has heat exchangers 102, 103, 104 which are arranged in the combustion gas flow section and recover the heat of the combustion gas; and the ammonia supply section supplies ammonia discharged from the ammonia fuel supply system to a position further downstream than the air supply section and further upstream of the heat exchanger.

[0123] The supply of air from the air supply unit intensifies the combustion of the fuel within the furnace, consuming more air. Consequently, the space downstream of the air supply unit has a lower oxygen concentration than the space upstream of the air supply unit. In the above configuration, the ammonia supply unit supplies ammonia discharged from the fuel supply system further downstream of the air supply unit. This allows ammonia to be supplied to spaces with low oxygen concentrations, thereby more effectively reducing NOx contained in the combustion gas.

[0124] Furthermore, because the heat exchanger recovers heat, the combustion gas temperature in the space upstream of the heat exchanger is higher than in the space downstream of the heat exchanger. In this configuration, the ammonia supply unit supplies ammonia discharged from the fuel supply system to a location upstream of the heat exchanger. This allows ammonia to be supplied to a space where the combustion gas temperature is high (for example, a space with a combustion gas temperature of approximately 1000°C), thereby more effectively reducing NOx contained in the combustion gas.

[0125] Furthermore, the boiler system according to a third aspect of the present invention, in the first or second aspect, includes a denitrification device that denitrates the combustion gas, and the ammonia supplier supplies ammonia discharged from the ammonia fuel supply system upstream of the denitrification device.

[0126] In the operating method of the combustion system involved in the first embodiment of the present invention, the combustion system includes: a burner 21D, which burns ammonia to form a flame in the furnace 11; a combustion gas circulation part 12, in which the combustion gas generated in the furnace circulates; an ammonia fuel supply system 210, which supplies ammonia as fuel to the burner; and a purge gas supply part 221, which supplies a purge gas to the ammonia fuel supply system to discharge ammonia from the ammonia fuel supply system. The operating method of the combustion system includes: an ammonia supply process, which supplies the ammonia discharged from the ammonia fuel supply system to the interior of the combustion gas circulation part of the boiler.

[0127] Explanation of symbols

[0128] 10-Boiler, 11-Furnace, 12-Combustion gas channel, 13-Flue, 20-Combustion device, 21-Burners, 22-Fuel supply pipe, 23-Wind box, 24-Air duct, 25-Additional air port (air supply unit), 26-Additional air duct, 27-Burner valve, 31-Fuel supply unit, 32-Forced draft fan, 41-Gas duct, 42-Air preheater, 43-Denitrification device, 44-Dust collection device, 46-Desulfurization device, 47-Chimney, 51-Ammonia nozzle, 52 -NOx detection unit, 53-Ammonia detection unit, 100-Boiler system, 100A-Boiler system, 101-Furnace wall, 102-Superheater, 103-Reheater, 104-Economizer, 200-Control device, 202-Ammonia control unit, 210-Ammonia fuel supply system, 210a-Fuel supply pipeline, 210b-Circulation pipeline, 211-Ammonia fuel tank 212-Pump, 213-Heater, 214-On / Off valve, 215-Control valve, 216-On / Off valve, 220-Ammonia supply System, 220A-Ammonia supply system, 221-Purge gas pipeline, 221a-Purge gas valve, 222-1st exhaust pipeline, 222A-1st drain pipeline, 222a-1st exhaust valve, 222aA-1st drain valve, 223-2nd exhaust pipeline, 223A-2nd drain pipeline, 223a-2nd exhaust valve, 223aA-2nd drain valve, 224-3rd exhaust pipeline, 224A-3rd drain pipeline, 224a-3rd exhaust valve, 224aA-3rd drain Valve, 225-4th exhaust pipe, 225A-4th drain pipe, 225a-4th exhaust valve, 225aA-4th drain valve, 226-ammonia recovery tank, 226A-ammonia recovery tank, 227-ammonia discharge pipe 227A-ammonia discharge pipe, 227a-control valve, 228-ammonia supply pipe, 228A-ammonia supply pipe, 228a-fan, 228aA-pump, 228b-flow sensor, 228bA-control valve, 228c-control valve, 228d-on-off valve.

Claims

1. A combustion system comprising: a burner, which burns ammonia to create the flame inside the furnace; a combustion gas circulation portion through which the combustion gas generated in the furnace circulates; an ammonia fuel supply system for supplying ammonia as fuel to the burner; a purge gas supply unit that supplies a purge gas to the ammonia fuel supply system to discharge ammonia from the ammonia fuel supply system; and The ammonia supply unit supplies ammonia exhausted from the ammonia fuel supply system into the combustion gas flow unit.

2. The combustion system according to claim 1, comprising: a nitrogen oxide detection unit that detects an amount of nitrogen oxides contained in the combustion gas flowing downstream of the ammonia supply unit; an adjusting unit that adjusts the amount of ammonia supplied to the interior of the combustion gas flowing portion through the ammonia supply unit; and The control unit controls the adjustment unit based on information detected by the nitrogen oxide detection unit.

3. The combustion system according to claim 1, comprising: an ammonia detection unit that detects an amount of ammonia contained in the combustion gas flowing downstream of the ammonia supply unit; an adjusting unit that adjusts the amount of ammonia supplied to the interior of the combustion gas flowing portion through the ammonia supply unit; and The control unit controls the adjustment unit based on the information detected by the ammonia detection unit.

4. A boiler system comprising: The combustion system of claim 1; and The heat exchanger is provided in the combustion gas flow portion and recovers heat of the combustion gas.

5. The boiler system according to claim 4, comprising: an air supply unit, which is provided at a position downstream of the burner in the flow of the combustion gas and supplies air into the furnace; The ammonia supplier supplies ammonia exhausted from the ammonia fuel supply system to a location downstream of the air supplier and upstream of the heat exchanger.

6. The boiler system according to claim 4, comprising: A denitration device for denitrifying the combustion gas. The ammonia supplier supplies ammonia discharged from the ammonia fuel supply system to an upstream side of the denitration device.

7. A method for operating a combustion system, wherein: The combustion system comprises: a burner, which burns ammonia to create the flame inside the furnace; a combustion gas circulation portion through which the combustion gas generated in the furnace circulates; an ammonia fuel supply system for supplying ammonia as fuel to the burner; and A purge gas supply unit supplies a purge gas to the ammonia fuel supply system to discharge ammonia from the ammonia fuel supply system. The combustion system operation method includes an ammonia supply step of supplying ammonia discharged from the ammonia fuel supply system into the combustion gas circulation unit.

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